Rotary screen for paper pulp



192 July 7 R. s. CLARKE ROTARY SCREEN FOR PAPER PULP Filed May 19. 1925 3 Sheets-Sheet l 1,635,258 July 12, 1927- R. s. CLARKE ROTARY SCREEN FOR PAPER PULP Filed May 19. 1925 3 Sheets-Sheet 2 TaZPZZi- July 12, 1927.

R. S. CLARKE ROTARY SCREEN FOR PAPER PULP Filed May 19. 1925 s Sheets-Sheet 5 Patented July 12, 1927.

, UNITED STATES PATENT OFFICE.

RALPH S. CLARKE, OF SOUTH WALPOLE, MASSACHUSETTS, ASSIGNOR TO BIRD MA- CHINE COMPANY, OF SOUTH WALPOLE, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS.

ROTARY SCREEN FOR PAPER PULP.

Application filed May 19,

This invention relates to machines for screening pulp and more particularly paper pulp. The invention is especially although not exclusively concerned with the type of machine in which the screen is mounted in a vibrating vat.

It is the chief object of the invention to reduce the expense of manufacturing and operating pulp screening machines and to improve the efficiency of such machines.

It is a particular object of the invention to eliminate, so far as possible, from the mechanisms that support and vibrate the vat, the parts having friction surfaces and which require lubrication. In a machine of this character such parts are subject to rela tivelyrapid wear, thus requiring frequent adjustment and ultimately necessitating renewal of the worn parts. The invention also involves improvements in the arrangement provided for removing from. the machine the waste material rejected by the screen.

The nature of the invention will be readily understood from the following description when read in, connection with the accompanying drawings, and the novel features will be particularly pointed out in the appended claims.

Referring now to the drawings,

Figure 1 is a side elevation, partly in cross section, of those parts of a. pulp screening machine with which the invention 15 more especially concerned;

Fig. 2 is a vertical, transverse, cross sectioial view of the machine shown in Fig. 1; an

Fig. 3 is an end view of the machine shown in Fig. 1.

The machme illustrated in the drawings comprises a cylindrical screen 2 which is constructed and mounted in the usual man ner. The right-hand end, Fig. 1, of this screen is equipped with a large annular bearing ring (not shown) which is supported in an end frame piece 3. The screened stock is discharged from within the screen through this ring and the discharge spout 5. The left-hand end of the screen includes a head 6 which is formed integral with, or is secured rigidly to, a shaft 7, and this shaft is -supported in an end frame 8. The end frames are mounted on a suitable base 9.

1925. Serial No. 31,297,

For the purpose of rotating the screen 2 a worm wheel 10 is secured to the shaft 7 and meshes with a worm 12 which is driven by an inclined shaft 13. This shaft is rotated by a bevel gear connection 1415, Fig.

, 3, with a driving shaft 16 extending longitudinally of the machine. The screen 2 is mounted in a vat 18 which is supported on two heavy brackets or girders 19 and 20. Referring to Fig. 2, it

will be seen that the opposite ends of the bracket 20 are mounted. respectively, on two upright laminated leaf springs 21 and 22. The lower ends of these springs are bolted to the bed 9 of the machine while their upper ends are bolted to the bracket. The bolts pass through slots (not shown) formed in flanges 23 and 24 so that the bracket may be adjusted vertically with reference to the springs. This adjustment is facilitated by thrust bolts 25 and 26 that project vertically through a part of the bracket in alinement with the respective springs 21 and 22 and bear against blocks 27 and 28 which are seated, respectively, on the springs. The other bracket 19 is similarly supported by laminated leaf springs 29 and 30, Fig. 3. The space between the opposite ends of the vat and the end frames 5 and 8 is closed by the usual flexible strips 31 and 32, Fig. 1.

For the purpose of vibrating the vat two eccentric mechanisms are mounted on the shaft 16, these mechanisms being in alinement, respectively, with the two brackets 19 and 20. The mechanism in alinement with the bracket 20 is shown in Fig. 2. It includes a leaf spring 35, one end of which is bolted securely to the central portion of the bracket 20, while its other end is bolted rigidly to a divided eccentric strap 36. This strap is oscillated by an eccentric 37 driven from the shaft 16, thus imparting a horizontal vibratory movement to the bracket 20 and hence to the vat 18, the direction of this movement being substantially at right angles to the axis of rotation of the screen. The other vibrating mechanism which is connected to the bracket 19 is exactly like that just described. Since there are two vibrating mechanisms operating in unison any tendency of the vat to swing about. a vertical axis is eliminated. The vat simply moves backward and forward in a trics in their adjusted positions.

substantially horizontal plane, the upright springs which support it flexing to permit such movement.

Preferably an adjustable eccentric mechanism is used so that the amplitude of vibration of the vat can be varied to suit different conditions. In the arrangement shown the eccentric 37 is angularly adjustable on an inner eccentric 38 which is keyed to the shaft 16. The latter eccentric has a flange 39 lying against the face of the outer eccen-. tric 37 and this flange is slotted to receive an adjusting bolt 40. This construction permits an adjustment of the angular relationship between the two eccentrics, after which the bolt is tightened up to secure the eccen- Consequently, the operator can adjust the effective eccentricity of the Vibrating mechanism and hence vary the amplitude of vibration of the vat within reasonable limits.

The vat 18 is constructed to maintain the screen 2 partially submerged in the paper stock to be screened, and the screening action is promoted by the surge of the stock produced by the vibration of the vat. The stock to be screened preferably is delivered to the vat 18 from a head box 42 which extends along the side of the vat and is supported by the end frames 3 and 8. A strip 43, Fig. 2,"of rubber or other suitable material closes the space between the stationar box 42 and the oscillating vat 18. The stoc flows over this strip 43 in a thin sheet extending substantially the entire length of the vat. Stock flows through substantially all parts of the screen that are submerged into the interior thereof and out through the spout 5, Fig. 1, at the end of the screen. The vibration of the vat, being in a horizontal direction, exertsa maximum tendency to force the stock through the screen at theopposite sides thereof while, at the same time, presenting a minimum of resistance to the natural tendency of the heavy waste particles in the stock to. settle to the bottom of the vat. through a long slot 45, Figs. 1 and 2, formed through the bottom of the vat, into the drain 46 and is carried away from the machine. The settling of these heavy constituents of the stock is also facilitated by the fact that the stock is delivered to the vat in a vertical direction from the head box 42.

The stock may be supplied at either side .of the vat, or under some circumstances This heavy material passes out' terial flowing over this weir drops on to a short apron 49 which preferably is made of sheet metal and is secured to the side of the ,vat, this apron projecting over a trough 50 in which the overflow is received and. carried away from the -machine. The apron covers the space between the stationary trough 50 and the vibrating vat.

In order to clear from the screen mats of fibre and other materials that tend to cling to it, I have provided a spray pipe 52 wh ch is supported at one end of the screen by a bracket 53 and extends for nearly the entire length of the screen, this pipe being located above the level of the screened stock in the screen. A series of holes is drilled through the upper side of the pipe to permit the escape of jets of water, and the pipe is equipped with a deflector plate 54 against which these jets strike. This plate causes the "ets to spread out in a fanlike formation so t at a substantially continuous spray is discharged through the unsubmerged portion of the screen for practically the entire length thereof. This spray clears the screen of foreign materials which adhere to it, and the spray, together with a considerable part of the material dislodged by it from the screen, is caught in a trough 55.

This trough is of approximately C-shaped cross-section with its open side toward the screen and it is located close to and just above the surface of the screen. It is supported at intervals by brackets 56, Figs. 2 and 3, these brackets being pivoted at 57 so that the trough can be swung away from the screen into an inoperative position whenever desired, as for example, in making reairs. Another trough 58, Fig.2, is located ust below the spray pipe 52 inside the screen where it catches any drip from the pipe.

ing of the screen by the spray is produced if the spray is directed through the screen after it has passed the highest point in its travel and before it re-enters the paper stock in the vat. The reason for this appears to be that if the cleaning spray is discharged either vertically or in an oppositely inclined direction to that shown, matted portions of stock which are dislodged from the screen but are not carried into the trough fall back upon the screen and-are again carried up to the jet or spray, where this action is re peated. In other words, these dislodged mats of fibre, if not carried into the trough, meet a portion of the screen which is rising and which brings them up to the jet again. This tends to cause an accumulation of such stock upon the screen immediately behind the jet. By locating the jet in substantially the manner shown, any action of this character is obviated since the dislodged particles, if not carried into the trough, fall upon a descending part of the screen which carries them into the body of stock in the vat.

It will be evident, therefore, that in this machine waste material or material rejected by the screen is removed from the screen in three ways,first, the heavy material settles and is discharged through the spout 46; second, the floating material is carried over the weir 48 and ejected; and third, rejected material which clings to the screen is cleared from it by the spray from the pipe 52 and is carried away in the trough 55. The removal of these rejected materials is important in maintaining the screen in a clean and efficient condition and results in an improved efliciency of the machine.

It should be noted particularly that the mounting of the vat in'the manner above described eliminates from the vat supporting mechanism all parts having friction surfaces, and which, ifpresent, would require lubrication. The use of the spring 35 in the vibrating mechanism for the vat also reduces the number of surfaces requiring lubrication in this mechanism. This construction not only-reduoes the amount of care and attention which the machine requires, but it also reduces. the rate of depreciation and it provides a machine which can be manufactured much more economically than prior machines.

While I have herein shown and described the best embodiment of my invention that I have so far devised, it is contemplated that the invention ma be embodied in other forms without departing from the spirit or scope thereof.

Having thus described myinvention, what I desire to claim as new is:

1. In a screening machine of the character described, the combination of a vat,

a screen in said vat, flexible supports formscreen,-a vat in which said screen is mounted, substantially upright springs at opposite sides of said vat supporting the vat in its operative pos1tion,. and mechanism for viv brating said vat.

4. In a screenin machine of the character described, the com ination of a substantially horizontal rotary screen, a vat in which said screen is mounted, two substantially upright leaf springs at each side of said vat, said springs supporting said vat in its op: erative position, and mechanism for vibrating said vat horizontally.

5. In a screening machine of the character described, the combination of a vat, a sub st-antially horizontal rotary screen mounted in said vat, flexible supports forming the sole means for sustaining said vat in its operative position, and mechanism for vibrating said vat horizontally, said mechanism being adjustable to vary the amplitude of vibration of the vat.

6. In a screening machine of the character described, the combination of a vat supported for vibration, a rotary screen mounted in said vat, a spring connected with said vat, and mechanism operating through said spring to vibrate the vat.

7. In a screening machine of the character described, the combination of a vat supported for vibration, a rotary screen mounted in said vat, a leaf spring rigidly connected at one end to said ,vat, and mechanism connected with the opposite end of said spring for operating through the spring to vibrate said vat.

, 8. In a screening machine of the character described, the combination of a substantially horizontal rotary screen, a vat in which said screen is mounted, two substantially upright leaf springs at each side of said vat, said springs supporting said vat in its operative position, another spring secured at one 100 end to said vat, and mechanism connected with the opposite end of said spring for operating through the spring to vibrate said 'vat horizontally.

9. In a screening machine of thecharacm5 ter described, the combination of a screen mounted to rotate about a substantially hor 1- zontal axis, a vat in which said screenus mounted, said vatbeing arranged to maintain the screen partly submerged in paper 0 stock, a spray. pipe within the screen extending longitudinally thereof and arranged to discharge a cleaning spray in an upwardly inclined direction through the unsubmerged portion of the screen, a trough of approxi- 1 5 mately C-shaped cross section located close to the screen but above and at one side thereof with its open side positioned to re- .ceive said spray, and means for supporting said trough for pivotal movement away from 120 the screen.

10. In a screening machine of the character described, the combination of'a substantially horizonta'l rotary screen, a vibratory vat in which said screen is mounted, means 125 for delivering stock to be screened into said vat at one side of the screen, and a weir at the opposite side of the screen over which floating material rejected by the screen may be discharged.

11. In a screening machine of the character described, the combination of a substantially horizontal rotary screen, a vibratory vat in which said screen is mounted, said vat being arranged to maintain the screen partly submerged in paper stock and having a slot in the bottom thereof for the discharge of heavy material rejected by the screen, a head box extending along one side of said vatfor delivering stock to be screened to the vat, a weir at the opposite side of said vat over which floating material rejected by the screen may be discharged, a spray pipe extending longitudinally of and inside the screen for discharging a cleaning spray in an upwardly inclined direction through the unsubmerged portion of the screen, and a trough external to the screen for catching said spray.

12. In a screening machine of the character described, the combination of a substantially horizontal rotary screen, a vibratory vat in which said screen is mounted, said vat being arranged to maintain the screen partly submerged in paper stock and having a slot in the bottom thereof for the discharge of heavy material rejected by the screen, a head box extending along one side of said vat for delivering stock to be, screened to the vat,

and a Weir at the opposite side of said vat over which oating material rejected by the screen may e discharged.

RALPH S. CLARKE. 

